(1) Field of the Invention
The present invention concerns a hygienic agent for use in hemodialysis.
(2) Description of Prior Art
The principle of the extra corporeal dialysis is based on the contact of the blood to be purified with a dialysate through a semi-permeable membrane. In order to obtain efficient exchanges, the blood and dialysate must be permanently renewed, since the speed of diffusion, or of dialysis, depends on the difference of concentrations between the blood and the dialysate. This is obtained by creating an extra-corporeal circulation.
Any dialysis chain comprises a generator, a dialyzer, a dialysate and a water circuit.
The generators enable to obtain the dialysate, the circulation of the blood and of the dialysate, and the controls of the parameters of dialysis.
The artificial kidney or dialyzer permits the elimination of water and of the waste produced by the body by contacting the blood with a liquid which is the dialysate or a dialysis bath. The blood and the dialysate are separated from one and other only by means of a thin artificial organic membrane, of cellophane, cuprophane, polysulfone, polypropylene, polyamide, polyacetate, copolymer of acrylonitrile . . . This membrane can be prepared in the form of plates, as compartments which are piled over one and other, or in the form of coils, as a single compartment which is spirally wounded about an axis or finally as capillaries consisting of an assembly of very fine hollow fibres.
Thus, there are three types of dialysis which are often delivered sterile for single use.
In the coiled kidneys, of the type where two sheets of dialysing membrane are spirally wound in a parallel fashion about an axis, the blood circulates inside the envelope defined by the two sheets of the membrane and the dialysate on the outside. The coiled kidney is actually the less utilized.
The plate kidneys are all disposed according to the same diagram corresponding to an assembly of 15 to 20 sheets of membrane mounted as an arrangement of plates in a sandwich type fashion, so as to provide inserted blood compartments and dialysate compartments. The blood circulates from. top to bottom between the sheets while the dialysate circulates in opposite direction.
The hollow fibre kidney contains very little blood; it offers a very weak resistance to the flow of blood. Instead of sheets of membrane in roller or plate arrangement, the dialysing surface is formed in the case of thousands of tiny hollow fibres. The blood passes from top to bottom and the dialysate passes around in the other direction.
The dialysate is a mixture of water and electrolytes, and the concentration of the electrolytes in the dialysate is provided so that the composition of the electrolytes in the blood is normal at the end of the operation.
For hemodialysis uses, water should be very pure and chains of hemodialysis are generally provided with a water treatment consisting of softeners, demineralizers, osmosers, filters and a container for storing water. After the container for storing water where is found a utilisation circuit which feeds the dialysis generators.
Since the appearance of the extra-corporeal blood purifying techniques, there were always problems associated with the disinfection and tartar removal from the material used.
The dialyzers are often materials considered to be for single use. However, certain establishments reuse them under the responsibility of medical doctors. Now the chain of dialysis can very easily be contaminated and this is the reason why it must absolutely be disinfected on a regular basis.
Clinical reports indicate that important microbial proliferations in hemodialysis apparatuses can have serious effects on patients who are dialysed. More particularly, such phenomenons as bacteremia, hepatitis, fever, shivers, hypotension and shock have been observed.
Hot sterilization which would represent the ideal hygienic step is actually not feasible because of the numerous elements of the chain of dialysis which are unstable with respect to heat.
The addition of impervious filters placed immediately before the dialyzer is not completely satisfactory, since virus, mycoplasma and certain bacteria can pass through these filters.
In addition these physical methods of disinfection require a regular chemical disinfection of the other elements of the chain of dialysis.
In view of all the requirements that an appropriate disinfecting agent should meet, namely a large spectrum of activity for an active time which is as short as possible, cleaning and material preserving properties as well as a capacity to be easily rinsed under controlled conditions, only certain compounds can be considered.
The products used for disinfection are generally formaldehyde or sodium hypochlorite.
The water circuit can be regularly disinfected with formaldehyde or with sodium hypochlorite.
This operation is generally carried out once every six months since it is time consuming and requires that the operation of hemodialysis be stopped.
Sodium hypochlorite is used under more or less substantial dilutions depending on use, of the order of 50%, for the disinfection of generators.
Formaldehyde is also used under more or less substantial dilutions depending on the intended use.
These disinfecting products require multiple manipulations, such as preparations and dilutions and involved risks. Thus, formaldehyde can produce an allergy which is well classified as a professional disease. Sodium hypochlorite brings in chlorine in a highly pure medium, which represents an inconvenience.
Independently in the disinfection, various acids are used to remove tartar, such as acetic, lactic, citric acids . . .
Peracetic acid, whose disinfecting properties are known, has been proposed at a concentration of a few percentages, from the order of 3.5-4%, for the disinfection of generators of dialysis. Under this concentration, this type of disinfecting agent has various disadvantages, including the fact of being a product which presents risks for the treating staff because of its irritating effect on skin and mucous membranes, as well as its corrosive activity on the dialysis material.
Therefore, a search has been made for a new concept of hygienic agent for use in hemodialysis which would meet the following conditions: non-toxicity and biocompatibility in trace amounts, combined disinfection and tartar removal, active time lower than 30 minutes, complete disinfecting effect, easily rinsable and detectable, biodegradable, stable and ready to be used.